The technical sector of the present invention is that of the devices used for firing various projectiles by means of a compressed gas.
To feed firing apparatuses such as weapons with compressed gas, a well known method consists in using valves or obstructors, located in a pipe, actuated by a percussion hammer so as to deliver a quantity of compressed gas required for launching a projectile. In most cases, a spring is used for returning the valve to its original position in order to provide for circuit tightness. As an illustration, the following patents may be mentioned: U.S. Pat. Nos. 3,527,194, 3,741,189, 2,940,438, 2,817,328, 4,116,193 and 4,602,608. This spring must be calibrated so as to take gas pressure into account and it is difficult to obtain an approximately constant quantity of gas, in order to avoid a too large dispersion upon firing. Thus, the use of this spring imposes some constraints and, moreover, in case of breaking, requires a complete disassembly of the weapon or apparatus.
On the other hand, in the patent FR-A No. 1 113 966, a compressed air operated weapon was proposed, in which the valve and its spring were replaced by a valve consisting of a flap and a seal providing for circuit tightness. In operation, the seal moves inside its housing and is compressed between two stops. This results in a quicker wear of this seal and in a compressed gas consumption incompatible with the use of a standard reserve of compressed gas.
The aim of the present invention is to propose a feeding service equipped with a conventional valve, which includes no valve return spring and which can be used with a standard reserve of compressed gas.
Therefore, the object of the invention is a device intended to feed with compressed gas a weapon including a gas reserve, a valve moving inside its housing, and a valve seat located in this housing, holding and guiding the valve rod, wherein said device includes an expansion unit interposed between the gas reserve and the valve, consisting of a first expansion chamber communicating with the gas reserve and a second chamber communicating with the valve housing, both chambers being separated by a calibrated orifice.
The volume of the second chamber may be 5 to 7 times smaller than that of the first chamber.
Both chambers may consist of hollow cylindrical elements.
The cylinder which constitutes the second chamber may be engaged into the valve housing, its end constituting the valve stop so that the distance between the seat and the stop determines the valve stroke.
The expansion unit comprises a sleeve which supports a perforating needle intended to pierce the gas reserve, the said sleeve including an open cavity into which the needle protudes and intended to accommodate the collar of the gas reserve.
A two-lip hollow seal is located in the sleeve cavity, the first lip being brought to bear upon the cavity bottom and around the needle, and the second being brought to bear upon the gas reserve collar.
An advantage of the present invention is that the valve opening-closing cycle, as a function of time, has a square profile. So, the full opening and the full closing of the valve are quasi-instantaneous.
Another advantage lies in that the weapon can be used in a temperature range varying from -15.degree. to +40.degree. C., which is not possible with a spring-loaded valve.
Another advantage is the simplified assembly of the valve since it is no longer necessary to provide two bearing points for the conventional spring, one on the valve itself, the other on a fixed point of the weapon.
Another advantage is that the quantity of compressed gas delivered is approximately constant in operation, which does not change the ballistics of the weapon.